Based on the monitoring values of seven heavy metals in the sediment of 8 State-controlled Sampling Sites in Huiwanzhong, Luojiaying, Guanyinshandong, Guanyinshanzhong, Guanyinshanxi, Baiyukou, Haikouxi and Dianchinan of Dianchi outer Lake during the ‘13th Five-Year Plan period’(2016—2020), the pollution characteristics and ecological risk assessment of heavy metals were carried out by using the methods of geoaccumulation index and potential ecological risk index, with Origin, ArcGIS, SPSS and other software. The results showed that the average contents of As, Hg, Cr, Pb, Cd, Cu and Zn exceeded the soil background values of Yunnan Province by 0.46, 4.70, 0.47, 0.73, 3.47, 1.17 and 1.13 times respectively, and the spatial and temporal distribution was different. In terms of time variation, the contents of As, Cd, Cu and Zn showed a general downward trend, among which As decreased significantly and showed a linear decreasing trend. In spatial distribution, the high contents of As, Hg, Cr and Pb were concentrated in the southern part of Dianchi outer Lake. Cd and Cu were higher in the eastern waters, while Zn showed a trend of higher in the north and south. The results of geo-accumulation index method and potential ecological risk index method showed that the heavy metal pollution degree and potential ecological risk were high in Dianchinan, Huiwanzhong and Guanyinshanxi of 8 sites, Hg, Cd and Cu were the main indicators of pollution accumulation and potential ecological risk. The results of heavy metal source analysis showed that As, Hg, Cr and Pb were similar pollution sources, preliminary inference as industrial pollution source; Cu and Cd were mainly from agricultural pollution sources.